In a single sheet capacitively coupled plasma processing apparatus, a susceptor and a facing electrode (upper electrode) have diameters a little bit larger than that of a substrate in order to improve in-plane uniformity of a density of plasma (especially, uniformity in a radial direction of a substrate) applied to a surface of a substrate to be processed on a susceptor (generally, lower electrode) inside a chamber. In this case, if a peripheral portion of a top surface of the susceptor which is projected outwardly in the radial direction of the substrate is directly exposed to the plasma, the peripheral portion is damaged and deteriorated by ion bombardment from the plasma. Especially, in a plasma etching apparatus, since ions are accelerated to be introduced by using a DC voltage or a self-bias voltage generated in the susceptor, an ion sputtering effect is increased. Therefore, the susceptor is protected from the plasma by detachably attaching a ring-shaped covering member, i.e., a so-called focus ring, so as to cover the peripheral portion of the top surface of the susceptor which is projected outwardly in the radial direction of the substrate (see, e.g., Japanese Patent Laid-open Application No. 2000-36490).
The focus ring is made of a material that does not substantially affect the plasma processing on the substrate even if part of the material is scattered around by sputtering. For example, Si, SiC, C (carbon) or the like is used in a plasma etching of an oxide film, and SiO2 is used in a plasma etching of polysilicon.
In the plasma processing apparatus, whenever the plasma processing is carried out, the focus ring sputters by the effect of the ion bombardment from the plasma, and the wastage thereof increases temporally. For that reason, the focus ring is considered as a consumable or a replaceable item. Since the focus ring is high-priced, a COC (cost of consumable) thereof deteriorates as a life span or an exchanging cycle thereof is shortened.
Recently, a high frequency power used in the plasma processing increases due to improvement in processing performance, processing time reduction or the like. Accordingly, the energy of plasma ions increases, and the wear rate of the focus ring increases. Especially, in a dual frequency application type in which two high frequency powers are superposed and applied to the susceptor, a high-density plasma is generated by a higher frequency power and ions are attracted to the substrate by a lower frequency power such that the energy of the ions bombarding the focus ring is further increased, resulting in a remarkable deterioration of the COC (Cost of Consumable) of the focus ring.